docs: def _layers_to_squash(self, layers, from_layer):
          """ Prepares a list of layer IDs that should be squashed """
          to_squash = []
          to_leave = []
          should_squash = True
  
          for l in reversed(layers):
              if l == from_layer:
                  should_squash = False
  
              if should_squash:
                  to_squash.append(l)
              else:
                  to_leave.append(l)
  
          to_squash.reverse()
          to_leave.reverse()
  
          return to_squash, to_leave